1. Field of the Invention
The invention relates to a common conducting unit, more particularly to a common conducting unit for a contact switch.
2. Description of the Related Art
FIG. 1 shows an exploded view of a conventional common conducting unit which is to be employed in a contact switch (see FIG. 2). As best illustrated in FIG. 1, the conventional common conducting unit includes a mounting plate 12 having an elongated flat portion 121 with two parallel end edges 1211, 1212, first and second end plate portions 124, 128 extending integrally and perpendicularly from the respective one of the end edges 1211, 1212 in opposite directions. The first end plate portion 124 has an engaging groove 127 formed on an outward face thereof and is parallel with the end edges 1211, 1212 of the flat portion 121. A common conducting leg plate 15 is formed integrally with the second end plate portion 128 of the mounting plate 12 and extends in the same direction as the second end plate portion 128. A spring engaging plate 123 projects from a position which is adjacent to the second end plate portion 128 of the elongated flat portion 121 in the same direction as the first end plate portion 124. The mounting plate 12 further has an opening 129 which extends from a position adjacent to the spring engaging plate 123 to a position adjacent to the end edge of the first end plate portion 124. The spring engaging plate 123 has a mounting hole 126 formed therethrough and a top end portion which is provided with a notch 125. A movable contact plate 13 has a pair of spaced leg portions 132 abutting pivotally in the engaging groove 127 of the first end plate portion 124. The movable contact plate 13 has an engaging opening 131 formed therethrough. One end 141 of the spring member 14 is hooked to the spring engaging plate 123 between the notch 125 and the mounting hole 126. The other end 142 of the spring member 14 passes through the opening 129 and is hooked to the movable contact plate 13 at the engaging opening 131, thereby enabling the contact plate 13 to move between an upper and a lower position when the spring member 14 is actuated.
Referring to FIG. 2, the contact switch includes a switch casing 11, first and second conductors 17, 18, a button member 19 and a press lever 16. The first and second conductors 17, 18 have downwardly extending leg portions which project out of the switch casing 11 in the same direction as the common conducting leg plate 15. The first and second conductors 17 and 18 have contact portions which are disposed inside the switch casing 11 and which extend respectively above and below the movable contact plate 13. The button member 19 is in contact with the intermediate portion of the spring member 14. The press lever 16 is actuated to push the button member 19 downward to correspondingly move the movable contact plate 13 to the upper position, wherein the movable contact plate 13 is in contact with the first conductor 17, or to the lower position, wherein the movable contact plate 13 is in contact with the second conductor 18.
The main drawback of the above described conventional common conducting unit resides in the mounting of the spring member 14. Since the mounting hole 126 of the spring engaging plate 123 does not lie in the same orientation as that of the engaging opening 131 of the movable contact plate 13, full automation of the mounting procedure of the spring member 14 to interconnect the spring engaging plate 123 and the contact plate 13 is difficult, thereby resulting in waste of labor, a longer production time and normally in low production. In addition, manual mounting operation results in poorer quality.